1. The Field of the Invention
This invention relates to apparatus used to determine the response of a patient to cutaneous stimulation. More particularly, the present invention relates to systems and methods for quantifiably determining a patient's responses to a variety of cutaneous stimuli in a repeatable and reproducible manner.
2. Technical Background
Many medical professionals and researchers have need to determine a patient's response to various modes of cutaneous stimulus. For example, medical professionals dealing with the human nervous system often need to determine a patient's response to various cutaneous stimuli to assess the extent of any damage to the nervous system due to trauma or a degenerative condition.
Still further, rehabilitation and physical therapists concerned with monitoring a patient's progress during recovery from a head injury, stroke, or some other event affecting somatosensory function also must conduct cutaneous or tactile testing. Moreover, primary care providers often desire to perform cutaneous testing as a routine screening procedure for their patients but have been unable to do so because of the specialized training, equipment, and experience needed to perform such testing using existing methods.
One area of particular interest and concern is the assessment and diagnosis of nerve damage affecting the function of the hand. Damage to the nerves serving the hand gives rise to a number of potential problems. In particular, there is a high level of concern over the increased incidence of carpal tunnel syndrome. Carpal tunnel syndrome gives rise to numbness, tingling, and pain, which often occurs when the person is away from the causative activity. This lack of relationship between the symptoms of carpal tunnel syndrome and the offending activity often leads to delay in identifying the problem and in seeking appropriate treatment. This delay may lead to increased injury and even permanent disability.
Within the last decade the incidence of carpal tunnel syndrome and related traumatic injuries have risen dramatically. The United States Bureau of Labor Statistics indicates that cumulative trauma disorders of this type were responsible for approximately 53% of the occupational illness reported by the private sector in 1989. Of these, carpal tunnel syndrome ranked second only to back injuries as the most frequently reported and most costly of Worker's Compensation claims.
Early detection of the problem can often prevent further damage and stop the progression of the trauma. It is apparent, therefore, that there is an increasing need for diagnosis and detection of carpal tunnel syndrome and similar disorders. Yet accurate and early detection has been difficult with known techniques and equipment.
Despite the clear need for repeatable, quantitative testing methods, evaluation of cutaneous function is normally done using manual testing techniques. Typically, the clinician stimulates the skin of the patient with one or more handheld testing devices, such as needles, tuning forks, hairs, filaments of varying stiffness, or dividers with varying separation between points. The patient then reports on the sensation achieved.
Manual procedures have a number of commonly recognized drawbacks. The clinician and, to some extent the patient, control the stimulus sequence, the interval between stimuli, the stimulus amplitude, and so on. The subject can obtain real or imagined cues from the clinician during the tests, and then second-guess in an attempt to improve or worsen his performance. All of these factors, which can have a significant effect on the outcome of the tests, may vary from session to session, limiting the validity of the resulting data. Moreover, other tests, such as those that measure vibrotactile threshold at different frequencies, temperature perception, and level of shape-dull awareness, are of diagnostic value, but cannot be readily and reproducible performed manually.
In designing testing procedures and equipment it must be remembered that normal cutaneous sensation is the result of central interpretation of sensory input from a mixture of receptor types in the skin. These sensations are mediated by a number of specialized and modality-specific nerve fibers. For example, touch and vibration sense in glabrous skin is subserved by at least four different types of myelinated nerve fibers. Temperature is subserved by two classes of fibers and pain by both the small myelinated and unmyelinated nerve fibers. It would, therefore, be ideal to have the capability of measuring independently, the performance of the three major modes of sensation
It is generally necessary to test all three of the principal modalities of cutaneous sensation, i.e., temperature, pain, and touch, in order to completely assess a patient's condition. As mentioned above, existing methods of testing the patient's thresholds and suprathresholds of temperature, pain, and touch involve manually applying the stimulus to the patient. Such manual methods are time consuming to prepare and administer, require a subjective determination by the administering technician, and are not consistently applied or reproducible from test to test.
In view of the foregoing, it would be an advancement in the art to provide apparatus and methods for accurately and reproducibility testing a patient's responses to one or more cutaneous stimuli. It would also be an advancement in the art to provide apparatus and methods for automatically testing a patient's response to various modes of cutaneous stimulation which does not require special expertise to operate and maintains a record of the results of the testing. It would be a further advancement in the art to provide a system and methods for automatically testing the cutaneous responses of a patient which imposes quantifiably accurate stimuli upon command and which carries out the testing in a relatively short period of time.
It would be of particular interest to provide a system which was able to control the amplitude, velocity, and time course of stimulation. It would be a further advancement to provide such a system which was designed to measure human cutaneous sensory threshold in a quick and efficient manner, thus being capable of rapidly screening subjects for early signs of sensory deficit. It would also be an advancement in the art to provide such a system which was designed such that neither the operator nor the subject was aware of the timing of the stimulus delivery. Finally, it would be a significant advancement to provide computer means for receiving data and for controlling the set of stimuli administered in order to obtain a predetermined data set.
Such methods and apparatus are disclosed and claimed herein.